Abstract
A multifunctional platform based on the microhotplate was developed for applications including a Pirani vacuum gauge, temperature, and gas sensor. It consisted of a tungsten microhotplate and an on-chip operational amplifier. The platform was fabricated in a standard complementary metal oxide semiconductor (CMOS) process. A tungsten plug in standard CMOS process was specially designed as the serpentine resistor for the microhotplate, acting as both heater and thermister. With the sacrificial layer technology, the microhotplate was suspended over the silicon substrate with a 340 nm gap. The on-chip operational amplifier provided a bias current for the microhotplate. This platform has been used to develop different kinds of sensors. The first one was a Pirani vacuum gauge ranging from 1-1 to 105 Pa. The second one was a temperature sensor ranging from -20 to 70 °C. The third one was a thermal-conductivity gas sensor, which could distinguish gases with different thermal conductivities in constant gas pressure and environment temperature. In the fourth application, with extra fabrication processes including the deposition of gas-sensitive film, the platform was used as a metal-oxide gas sensor for the detection of gas concentration.
Highlights
Complementary metal oxide semiconductor (CMOS) compatible sensors have been widely used in the detection of pressure, temperature, acceleration, and chemical leakage [1,2,3,4]
The microhotplate fabricated by microelectromechanical systems (MEMS) technology has been widely used for gas pressure sensors, gas sensors, chemical sensors, flow sensors, and accelerometers [8,9,10,11,12,13]
Tungsten has been traditionally used as a plug material to form via pathways between various metal layers due to its ability to uniformly fill the high aspect ratio vias when deposited by chemical vapor deposition (CVD) methods
Summary
Complementary metal oxide semiconductor (CMOS) compatible sensors have been widely used in the detection of pressure, temperature, acceleration, and chemical leakage [1,2,3,4]. The microhotplate fabricated by microelectromechanical systems (MEMS) technology has been widely used for gas pressure sensors, gas sensors, chemical sensors, flow sensors, and accelerometers [8,9,10,11,12,13] It could be implemented in the standard CMOS process for high yield and low cost. It has been employed to develop a Pirani gas pressure, temperature, and thermal-conductivity gas sensor based on the fact that the gaseous thermal conduction is mainly affected by gas pressure, gas temperature, and the type of the gas Besides those applications, with a little extra fabrication process, including deposition of the gas-sensing film on the microhotplate, this platform could be used as the heating component for a metal-oxide gas sensor
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